Setting and Retrieving Properties and Metadata for Blob Resources

Updated: February 26, 2015

Containers and blobs support custom metadata, represented as HTTP headers. Metadata headers can be set on a request that creates a new container or blob resource, or on a request that explicitly creates a property on an existing resource.

Beginning with version 2009-09-19, metadata names must adhere to the naming rules for C# identifiers.

Names are case-insensitive. Note that metadata names preserve the case with which they were created, but are case-insensitive when set or read. If two or more metadata headers with the same name are submitted for a resource, the Blob service returns status code 400 (Bad Request).

The total size of the metadata, including both the name and value together, may not exceed 8 KB in size.

Metadata name/value pairs are valid HTTP headers, and so they adhere to all restrictions governing HTTP headers.

The PUT operation sets metadata headers on the specified container or blob, overwriting any existing metadata on the resource. Calling PUT without any headers on the request clears all existing metadata on the resource.

The URI syntax for setting metadata headers on a container is as follows:

Containers and blobs also support certain standard HTTP properties. Properties and metadata are both represented as standard HTTP headers; the difference between them is in the naming of the headers. Metadata headers are named with the header prefix x-ms-meta- and a custom name. Property headers use standard HTTP header names, as specified in the Header Field Definitions section 14 of the HTTP/1.1 protocol specification.